Non-traditional metrics: PDO
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08-12-2012, 07:26 AM
Join Date: Dec 2006
Location: Waterloo Ontario
Originally Posted by
The PDO disbelievers would expect the hot weather to continue forever and use the 15 days as proof. The PDO users would expect the average temperature over the next 15 days to be 20, for an average of 25 degrees.
If you flip a coin 100 times and it comes up 75 heads and 25 tails, you don't bet that the next 100 will be 75 tails and 25 heads. You bet that there will be 50 heads and 50 tails, or 125 and 75 total. Flip the coin until you have 1000 results and the PDO users would expect there to be 525 heads and 475 tails. Do it until there are 10,000 results and the expected split is 5025 and 4075.
If you flip that coin 1 million times, the expected result would be 500,025 heads, 499,975 tails. Instead of 75% of results being positive, only 50.0025% are.
You are of course assuming that the coin you flip is fair. What if it is not? This is part of the problem with PDO.
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